CK-12 Foundation
Ck 12: Life Science: Lymphatic System
[Free Registration/Login may be required to access all resource tools.] If pathogens get through the body's first two lines of defense, a third line of defense takes over. This third line of defense involves the immune system. The immune...
BiologyWise
Biology Wise: Gram Negative Bacteria
Learn about gram staining and the characteristics of gram-negative bacteria. A discussion of cell wall structure is accompanied by a labeled illustration. Includes a list of examples of gram-negative bacteria organized by subgroup....
BiologyWise
Biology Wise: Eubacteria Examples
Presents examples of eubacteria along with descriptions.